CORN INSECTS 221 



aphids from the weeds to the corn roots and also seize any of 

 the winged migrating forms that come their way and carry 

 them down to the roots. In this way the corn soon becomes 

 badly infested. The injury is ordinarily first noticed in irregular 

 patches usually on the lower ground. The loss of sap caused 

 by the feeding of the aphids lessens the vitality of the plant, 

 causing the leaves to turn yellowish or reddish. The aphis is 

 most destructive in years of drought because under such condi- 

 tions the plants are least able to bear the loss of sap. Corn 

 plants badly stunted by the root-aphis often fail to bear ears 

 or produce only nubbins. 



Control. 



Experiments and the experience of practical corn-growers in 

 Illinois have shown that the losses caused by the corn root- 

 aphis may be in large measure prevented by plowing land 

 intended for corn to a depth of six or seven inches early in the 

 spring followed by thorough and repeated disking to break up 

 the ants' nests and scatter the eggs of the aphis. This treat- 

 ment also destroys the weeds on which the root-lice get their 

 start. It also puts the soil in good tilth, making possible a 

 strong and rapid growth of the corn. Corn is most likely to 

 be injured by the root-aphis when the crop is grown on the same 

 land for two successive years. Much injury may, therefore, 

 be avoided by adopting a rotation in which corn does not" 

 follow corn. As a supplementary treatment, S. A. Forbes 

 recommends the use of oil of tansy applied to each hill as a 

 deterrent for the ants. One fourth pound of oil of tansy 

 and 1 gallon of wood or denatured alcohol is mixed with 

 100 pounds of bone-meal. This is enough for an acre and 

 should be applied with a fertilizer dropper attached to the 

 planter. Careful preparation of the soil and thorough culti- 

 vation will tend to make the plants able to outgrow injury by 

 root-lice. 



